Storage Tank Fires

Storage Tank Fires: Is Your Department Prepared?

YEaY~MON?l3SORSOIREADMEITHERANEWS paper dipping or trade jaurnal about a perroletun produet stmage tank &e oodurring in the United States

or internationally. These fires have mmmed on the West Coast, the East Coast, and cities in between. The most spectacular fire occurring in past years w a s the 2005 Hatfordshire OiI Storage Terminal Fire (Bunoefield Oil Depot) in England. Most of the

fires I have read about that irIV0l~e petroleum product storage tanks contain a common element that municipal fir&@- ers gemdly overlook: Municipal ur volunteer Mghters elther £aught the fire ar supported the firefight. Although we train daily on our bread-and-butter operations and terrorist incident response techniques, we g e n d y neglect aaWng rm industrial hazards within our districts. Mimy &paxrmam~

have storage tanks in their Wets that fmiighters hive newt c l d y examined, yet they carefully inspect buildings under cons&uction 'to examine the conm-uction features and preplan their response in case of a fire. Too often, we take for granted the industrial sites in our dkiricts as just part of the 1-pe.

In the early days of the petroleum Inducitry, tank tanka were common. As the industry matured, it demanded beuer design, construction, fire protection, and impmvements to the various codes and ~~ maintained by the American Petroleum

Imettute an8 the National Pire Protection Assodation 0, resulting in far fewer tank Iks today than in the past. But they do happen!

It b interesting to note that although the frequency of tank hes has decreased, the size of the tanks have increased, pre- senting a more 6- hazard in the event of a fire. h a r e d

of t!ae in- in size, fires invohring large aboveground storage tanks can be extremely msdy in terms of property damage, bushes interruption, environmenml damage, and public opinion. Additionally, the control and atinguishment of full surface tank require a large amount of cornmi- fn human logistics and equipment resources. Because of the potential of a loss, the fw p m o n Industry has improved its techniques to effectively control md exxhgujsh fires in large-diameter storage tanks. These methods are ~~ u-. This article exan-dnw atmo$pherlc stmage bdc types, types of fires that you may encounter, preplannlng, and sug- gested 'Cactics.

a N B R A L DEbCWPTiON Flammable and combustible liquid storage tanks are found

in indmtrhl Eacillties such as &eriies, -edd hdi- ties, bdk storage plarlts, and m a d e te ' ' . Power plants, &ports, local fuel companies, and large manufacturing fa&- des such as automotive and steel plants may also have hk storage of flammable and combustible liquids.

Atmospheric storage tanks are used to store or mix flammable and oombustib1e liquids in various wys, depending on the kilities. These tanks can m g e 10 feet to more than 350 feet in dimetef and haw an average height of about 45 feet. Such can hold mare than 1,s d t o n barrels (6 mlt- lion gallons; for crude oil and other -1- products, one barrel equals 42 @ m I of flammable or comhwtlble liquids. Larger facilities rnay have rnore than 100 tanks of varying sizes and quantities, ccmtaining various products, which may be near each other and have several other tanks within a cmn- mon dike.

Dikes are physical barriers used to prevent the s p e d of tank contents if the tank overllows or the tank fails s m w - ly. IHWS are also wed to segregate and group tanks according to their c~ntmts classifcation. 'ihey rnay be made of mmpadd

&t {emhen dike) or concrete and similar type materials. The dike's height and perimeter are functions of the volume of the tanlts endosed within a particular dike. M m y dikes are d e signed to contain the toml contents of the tank plus a cerrah percentage dlwve this as a safety margin. This margin typically anticipates the ~ m u k i o n of frref~&ting water during erner- gendes. If more than one tank is enclosed within a common dike, tbr: dike should be able to contain at 1- the volume of the * p h a safiety m.

(1) A storage tank full surface fire at a petroleum storage facility. (Photos courtesy of Williams Fire & Hazard ton t rd )

FIRE ENOINWIIIW November 2008 b3

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STORAGE TANK FIIRES a ~ ~ T A N K r r p r s

< Tanksare-bedbytfleird

eating d; d domed external eating m f . The storage tank type

and the tank's lomtion (B-g., farm or a gasoline service

m e r low-pressure vertical or horizontal tanks, or underground tanks. Plmmable liquids are usually stored in open-top or intend b t h g m f t a n k s In bulk quantities, in small low- pressure vertical or horizontal tanks, or in underground tanks. (2) Flooding can affect firefighting a%-s and apparatus placement.

F d ~ ~ . Fm%-mf tanks @re vertid steel cylinders with a -permanently attached mf. In the petroleum and petrochemi- rim-seal space b the area the tank shell wall and the 4 industries, these permanent roofs are usually cone shaped internal floating roof (the difference in the mnk shell diameter w d are sometimes referred to as "frxed-mne roof" tanks. Such and the internal roof diameter). This rim seal area is usually - ~ f s are flat or slightly domed to prevent water accumulation one to four feet and may be the origin of m e fires. T h ~ e , and to pemdt a vapor space between the liquid's surface and tanks are typically used to stme highly flammable finished

' 7 APE standards and h e a weak roof-to-shell seam. In an 7- such as internal oveqmsure from an explosion or a t e d ) flogtifig roof tanks are v d d steel cylinders with a ' , , +similar situation, this design allows the roof ta separate from roof that floats on the surface of the liquid in the tank, but # &e vertical shell to prevent fallwe of rhe boaom scams and is open to the atmosphere above--i.e., there is no fixed m# -xhe tank's "rocketing" or pmpelhg upward. a h w . The only main difference between internal (covered]

is the presence of the &xed ~oof above to protect it from th& , Fixed-cone roof tanks include some foran of venting capability atmosphere. As with internal floating roofs, d m e Mnks havg

' bacuum vents. Presure-vacuum vents allow the pressure the changing of the liquid level. These tanks also have rim .

within the tank to remain ewal to the extend Atmospheric seals to prevent the vapors from escaping. ~ . D e p e n d l n g o n ~ e l o o p t m o f t h c a c r a n l u ~ ~ Domed mtemal floating rcmf tanks. Domed external respect to the community, these vents can be equipped with floating roof tanks function similarly to internal floating mof

i ,environmental contple,>vd le,~~~ap-sterkdiverbm to capture tanks and are created by mtmfitting a darned covering over fugitive emissions. an exhtlng external floating roof t d . These domed roof

(~o~cred) floatkg Ad. ~nfsrm~ ( c o v m x ~ tanks are o ~ e n r e f l e d m as gmdesic b e tanks.* ~hc floating roof tanks have a permanent bed rmf with a floating dorneys main purpose is to provide protection from the ele- ~mf inside. Internal floating roof tanks usually have vertical ments, but it also pravides environmerital control for fugitive

i ' ~suppom within the tank far the fixed roof ox have a self-sup- emissions. During the early stages of firefighting operations .porting 6xed rmf. The Internal rmf? also known as a *pan," at these tanks, the panels should melt away, and the support-

I ; $floats on the surhce of the liquid and rise& and falls with the ing fram%mrk should be the only obstruction. As the fie changing I d . The pan either floats on pontoons or has a continues to burn, the supporting framework will most likely

; "uble deck for flotation on the liquid surface. fold in and collapse onto the burning fuel surface. The large I The fured rmf above has openalx vents t~ permit the space Atmospheric Storage Tank Fire (JA!XHRE) project recorn-

( above the internal roof to breathe. Ftged roofs axe aUowed to mends that for any ddpated obstruction of full-surface fire vent in this manner because their vapor space is considered foam application, a higher application sate is required and

L :below the fhrnmablb limits. Seals are provided in the rim- preincident rsponse plans should allow for these higher ap

STORAOE TANK FIRES COMMO# ItPSPOH%E scmAm05

There are certain related hx hazards cornman to the various types of tanks. These hazards vary in sererig from a simple vent 6re to a fidl liquid rmrfarse tank &.The most common of these mcidents indude an o d l l ground fire, a vent he, a rim-seal fire, obstructed full liquid surface fue, and an unobstructed full liquid d c e fire.

Oveifill grwrnd fue. Ove15ll ground fires, or dike l%w,

mdt from piping or tank leakage. Many tlmes, they are the result of another cause, such as operator error or equipment malfunction, and are considered the least severe type of ha- dent. lf a leak occurs without igmtion, exerdse caution and isolate all ignition so-. If ignition does occur, then simply treat such a fire as a large pool fire. Overfill ground fires are common to fixed-cone roof, internal floating Mof, exsend floating roof, and domed roof tanks. Vent &ei. Vent fires are typicaliy mockted with bed roof

tanks such as cone and internal floathg roof tanks. The mah cause is a lightning strike that ignites fugitive vapors which may be present at the vent. This is a less severe type of lire and mn usually be -bed with a dry chemical fire ex- tinguisher or by reducing the pressure In the tank.

Rim-seal fires. Rim-seal fires comprise the large majority of fires in external floating roof tanks but a n occur in inter- & floating rmf tanks or domed rmf mnks. As with many tank fires, lightning is the primary cause of ignition, although

with floating roof tanks, an induced electrical charge without a direct lightning hit may QCCW Because these fires are the most .common, there is usually a high rate of successful extinguishment, assuming that there is no collateral darnage such as a gontom failure (explosion) ar the floating roofs sinking as a &t of fire suppression efEorts. Successful rim-seal fire extinguishment can be mostly attributed to the Installation of *-seal fire protection systems, such as foam chambers. These semi- or fully fured rim-seal fire protection systems have a gmd history of extinguishment, assuming proper design, insbhtion, and maintenance.

Rim-seal fires for intanal floating roof tanks are slightly mote challenging, espeday. if semi- or fully systems are nat provided. Thls means that the only access to the fire area for the application of fwe extinguishing media is through the

vents or access c m m . Obstmcted full Siquld h. Obstructed full

liquid surface fires can =cur in fmed-cone roof, internal hating roof, or external floating rwf tanks. Thgr tend to

be challenging because the roof or pan blwks access to the burning surface. The roof or pan can sink for various rea- sons, such as an increase in vapor pressure under an internal floating roof, which can =use the pan to tilt. Pontoon failure of external floating roofs Is commonly caused by closed d r - valves during rains or mechanical sed failure, causing tlw pan to sink.

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U-firllHHd mwface W, UfioQmmd lfqui4'wrface ' m i m r d a w e d y ~ m ~ h where tank d h l w r is d&miy ,mdl t hn 110 feet) md &dent ~ u m e s a n d ~ p ~ a t e ~wdabk The'most & ~ ~ . f i t . e s dl Invahrelmgm tanks &materthn 150 feet h &a&-] be@=,& the A@-wfa~ m a af the fk d be, amount , q P r e l m ~ ~ e B to tmtml $ad &bg&h the fire. UnobsbcW full s i i rhrnhmoceu l :hhd-mof 'kuh -'iratmId w, 'hgdde w d s - at* i ~ d m j . i a t ~ ~ m a W t & a n m p f + & n W P r t h e P ~ - d I w - ~ & f r l l I ~ b & . ~ m ~ W ~ ~ ~ ~ ~ r o n a t o ~ $mi&dWlWweh-heaw * cmdltlm. %ih closed d &&IsF * mf can quickly sink, lw-in& the q c w d UquM surfa- whwible ta a. ~~~*

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STORAGE rANK FIRES ideal conditions. Terrain wlU also affect containment and control of water runoff and other by-products of the tanks. FMghters walking through deep water or foam solution may trip and fall. Tank fires may require large volumes of water, which may overflow the containment areas. How and

(3) Foam totes are usea w uangport and store foam concentrate.

sooner than welded Canks when exposed to fire. In a gmmd fire in the dike area, you would want to know if there is q plping in the area, what it is made of, and how a fire will affect it.

In the case of mnks exposed during fire, they will ps i - bly have to be cooled. It is now an accepted theory that you should not cool the tank on fire unless you can cool it evenly all around for 360". Uneven cooling will allow the tank shell to fail in the area where the uneven cooling was applied.

Cbmpcy. Is the occupancy just a storage facility with a limited number of tanks? Or ape the mnks part of a industrial operation that may be affected by a spreading fire? Perhaps the overall operation L a greater hazard than the tank on fire-should you concentrate on protecting other aspects of the industrial operation?

Apparatus and staffing. Is your fire apparatus equipped to perform fireiighting on a storage tank? How much foam do you any? What size and type monitors are available, and are they apparatus-mounted or portable? How many persons respond from your department? Tank fires will usually require large volumes of water and many gallons of foam concentrate. Even if you have the equipment and foam, do you have the staf6ng to deploy these resources?

Wfe hazard. This is your number-one p r i o Consider not only the facility employees but also the surrounding community as well as your hefighting personnel. ICs must account for facility employees and contractors who may have ken working in the area. How does the facility account for the workers and contractors on site? Whom should the IC contact on arrival to determine if everyone at the facility has k e n accounted far? How many employees are normally on dury in the facility, and what are their primary, usual work areas?

Terrain. T e d n issues may be of concern during in- dwdrld incidents. Apparatus and portable ground monitor positioning can be seriously affected. A recent major tank h occurred during a severe rainstorm. Flooding of surrounding areas and access routes to the tank's location delayed response and dictated apparatus positioning in less than

where will this overflow travel once it becomes uncontained? lhes it contain flammable by-prducts that can then ignite and spread the fire?

Water supply. Water is critical at most fires. Industrial fires require large volumes of water for extinguishment, cooling, and vapor suppression. Can the area or plant fire water system supply the volume of water necessary to sustain an effeave attack on a fuel stotage tank7 If not, where and how can you obtain the additional water?

Even wlth an adequate water supply, departments must lwk at the delivery methods. Do you have enough large-diameter hose (LDH) to supply and deliver the water to the point of at-

tack? If your plan is to mil surrounding departments to assist with LDH requirements, are your hoses and theirs compati'ble? If they respond with fm-inch LDH and yaur department uses heinch LDH, are there enough fittings (four-inch to five-inch) to make connections where required?

If needed, can you conduct drafting operations to deliver the required quantities of water? Or are large-capacity pumps required for drafting and suppky? Recent advances in technology allow for positive intake to pumps when the pumps are located a distance From the open water supply. Hydraulicdy driven pumps can be lowered into tfie water, and then these smaller pumps can supply water to the larger pumps at ps i - tive intake pressures. This eliminates rhe need for placing large-volume pumps or pumpers dose to the open water sup ply for drafting purposes.

Auxiliary appliances and aids. Auxiliary appliances and aids are the systems and equipment that may be on the premises or in an indusrrial facility complex. Storage tanks may have foam systems installed to asstst with fire-ting ef-

forrs, mast particularly with rim-seal fires. When preinadent response planning, identify and evaluate these systems. Who will activate the system, and who d l supply the necessary water and foam to the system? If your department is tasked with supplying such a system, are you prepard? Develop a standard operating procedure and conduct annual W s on supplying such systems.

On arrival at an industrial facility, plant personnel can provide valuable assistance and advice. The IC should identify these persons in preincident response plans and include their contact telephone numbers and hours of availability.

Street conditions. General accessibility must be included under street conditions. Many industrial compIexes or storage tank facilities may be located in ateas away from residential centers. Roads may be narrow and winding. Inside facs~es, access mads may also be narrow, Depending on the size of your apparatus, this may affect response and placement. If your strategy indude6 using hge-cdiber streams from an aerial platform, does the street width support such operations? Apparatus placement may b l e streets, preventing the

I 68 November 2008 FIRE IWO*YEMO www.FimEngin~ring.com

STORAGE TANK FIRES passage of other vehicles needed for foam resupply or hose placement. Where drainage $wales (deep depressions in road- ways to facilitate drainage) are present, apparatus may not k able to cross them because of the length of the apparatus and wheelbase dishnce. Apparatus may lmttom out as they attempt to cross the depression. This must be determined during preinddent response plan*.

At a recent ddl, the original qpratw positioning did not aUowproperoutriggefplacementmdthushadto~changed, M v e l y bl-g the mad for placement of other apparatus. In addition to overall width and length of appctratus, edu& turn-

ing radius to ensure apparatus a n be positioned where Reeded Weather. Weather conditions can n o d fire depart-

ment operatiom, apedally at large tank fires. Winds m y carry the large volumes of smoke prcduced long distances. The absence of wind or the presence of heavy fog mn create cadi- tions where ihe smoke lies low in the area of operations. Heavy rains may awe flooding, affedng reqmnse and apparatus placement. Ibimme cold and heat cond].tiom require more fre- quent rehabibtion. Heavy r;lins may also break down p r o m tive foam blankets and cause dike areas to overflow. How can this water be removed h m the dike areas when necessary, and where will it be dhcted? Plant systwns or portable pumps may be necessary. Anticipate these needs prior to the incident.

Exposures. What exposures must be protected at a storage tank fire? Normally, exposures downwind are the first priority and those to the left and right of the downwind

tank wiIl also need some measure of cooling. One point to

highlight is that excessive coding water may overtax plant systems designed to remove storm water. A loss of power to the fdity's wastewater pumps may cam runoff water to back up into the fire area and overflow dikes or other con-

tainment measures. Cooling streams on exposures should be applied only as

long as the cooling effect of the stream on the exposed tank shell produces steam. Once steam is no longer generated, stop cooling measures. Restart when Ihe tank shell begins to heat up again. This conserves water for firefighting use and reduces runoff water. Cooling water for exposed tanks can be calculated in the following manner: "

-Atmmpheric storage tanks up to 100 feet In diameter require 500 gallons per minute (gpm).

-Atmospheric storage tanks Mween 100 feet and 150 feet in diameter require 1,000 gpm.

-Atmospheric storage tanks exceed@ the diameters listed above require 2,000 gpm.

Area. When we think of fire area, we normally think of length times width. In this Instance, we will use area to

highlight the size of the tanks that may be on fire as well as exposed tanks. A quick calculation that can be used for the square footage of a circular tank is the formula 0.8 x tank diameter. Dike areas must also be calculated by using length times width minus the square footage of the tank Inside the dike.

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r Explosive Hi j h storage cost

70 November 2008 FIRE ENGiNEERlNO www.FireEngineering.com I

Locat1.m and extent. During preincident response planning, identify areas of likely fire scenarios (lamtion) and worst-case scenarios (extent) to further asstst with identifying the re.wwces that may be needed.

'Pime. As with any or emergency, the time of day may affect res-. During certain times of the day, plant pasonnel who can asist may not be present. During other times of the day, opations that take place at the Wty may be more hazardous, Inmasing the risk of fire. These fires will be extended opaations and, in some cases, of campam length bltiple days). Is the faciIity adequately Ughtd, or does your preinadent response plan have to indude Mgl-intensity scene lighting? If you bring in portable scene lighting after an operation has started, access routes may be blocked by apparatus and h-. The time to identify this need is earb in the operation so you can ensure its placement before access mtm are blockd

~ t i m e o f d a y m a y a h a f f e c t t h e ~ o n o f s u m o u n d - i n g ~ e g i t h l s ~ ~ . ~ d d i a l a r e a s ~ c o n ~ m m p e o p l e n e d n g e v a c u a t i o n ~ g t h e ~ hours. Working at night cran also slow down lird@h& actions andcan~safetyifhamdousareasarenotQhtedeK&ively,

Height. A storage tank's height will a f k t operations. D"s your department have portable monitors that can delh.er streams to great h-7 The stream's trajectory Is important in m-the-top applimtion of hdighting streams. Tm far from the bank,andthestreamwillnotmchwerthetop;tooclose,d

you place yo& in a -us opaating position and the

SIORAGE TANK FIRES stream will not land on the fuel surface in a desired position.

special cord ti^. Identify anything else not prWiow1y mentioned in this section. Hazardous materials present, spe- c i a h d ismghhQ techniques, process cmmol opemtions, contingency or fadlty emagency re- plans that may be in place, and external resmmm such as m e d contracwrs

that may be required axe some of the items covered here. Rernemk, the more information you can gather prlor to the

incident, the easier it is to develop the inddent adon plan.

On notification of a storage tank emergencyJ the fire department should immediately begin gathering infomation and assessing the Incident. Although it has k e n said that size-up begins with the notification of the alarm and continues until the last unit h a left the scene, size-up d y begins with the prehident response planrung. The Information gathered at this stage is the foundation for all slze-up, stmtegy, and tactics used at these incidents. After using the pxeinadent response plan and the initial aIarm information, gather additional inforrnadon quickly wMe en route to and after arriving at the scene to develop an effecthe strategy to fight the m. Consider the following:

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STORAOE TANK FIRES

(4) Large-volume monitors and large-diameter hose are required to battte a large tank fire.

lwhguishmmt. mEnvironmental impact. *Community impact. AFteF address- the immediate issues, determine the type

of fire: vent, rim-seal, piping/connection, full involvement, overfill, tank and dike, multiple tank, or expsure.

Determining the type of fire will determine the resources required and dictate the necessary Incident action plan to

I frght the fire. There are several types of fires that an emergency organization could face and different ways of attacking than.

You can treat ground or dike fires d t i n g from tank overfilling or pipe failures as simple spill or pool fires. Trying to calculate the area of the oddly shaped spill mn be chal-

c u r d and foam operations are ongoing, entry in the dike should be forbidden. Disturbing the foam blanket can have disastrous effects, and hefighters should never enter into spilled product. You can usually extinguish fires involving the rim-seal area

with the semi or fully fixed water/fmm system. Response to this type of fire is similar to that of fires in sprinklered buildings in that you support the fixed systems on arrival. The main difference is that you should not attempt to extinguish the fire until you have confirmed the reliability of the water and the foam supply and that sufficient quantities of both will be available for the duration of the firefight. Remember, during preincident response planning, you must identify and evaluate these systems. You must also Identify whom to con-

lenging, but the k t tactic is to establish an adequate water and foam supply and begin to suppress the fire after adequate resources are on the scene. A common mistake is to try to extinguish such a fire with inadequate resaurces. If the fue is not -bed with 'the on-scene resources, it will continue to burn a d destroy the foam blanket already In place, negat- ing any positive impact you may have had. You can protect expsures such as the rank and associated

piping and pumps with water using ground monitors or those installed on hydrants.

Firefighters should not attempt to enter the dike area unless it is safe to do so. This mn be verified by atmospheric testing and ensuring that any spill potential does not fill the dike flm. This is especially true for small spills, with or without ignition. For larger spills, where ignition has oc-

tact to activate them. You marst test the use of these systems before, not during, an incident. Work with the plant personnel during the preincident response planning, and hold annual drills and exercises to practice supplying and activating the systems.

If semi or fully h e d systems are not hstdled, you can use portable equipment to extinguish these fires. You can use hoselines and monitors to fill the rim-seal area with water/ foam solution. Some tools, such as the Daspitm tool, are spe- c i f idy designed for rim-seal fues. 'Zhis monitor device has a braoe/ciamp attachment designed to secure it to the tank shell at the top Iip of the tank. You can also use it for other a p plicatiws. For oh& fmf&ting service applications, you can attach the Daspit Tool to a ground stand or a s a d mounted in the back of a pickup truck or other vehicle. The foam/water

72 November 2008 FIRE ENOIISEERINO www.FimEngineering.com

solution flaw rate for rim-seal fires using portable equipment rangesfPom25Q$pmfordsizetanks(upto9Of~in diameter) to 550 gpm for medium size tanks (90 to 175 feet in diameter] and 950 gpm for larger size tanks (175 to 300 feet in diameter;) with an appliation time of 20 minutes. The method of extinguishing tanks fires in manual op-

erations, using portable or mobile monitors, is comrndy referred to as T y p UI appkation or "over-thetop." Consider the following when using the over-thetop method: minimum application rates, application densMe.9, inhhnum foam solution application durations, and supplemmtal foam application rate in dike area.

These considerations vary based on fuel aash point, water imrniscibiity, type of foam, and applicatl.on device. Por fries involving h y d r o a r b s such as gasoline or diesel, a three- percent concentration is the Industry standard. P o w are now being used at mepercent concentrations. These have pwven v a y e f fdve in tests. For fires involving polar solvents such as dwh& or methyl-terhq buty1 ether @ITBE), w r t i o n three pexcenvsix percent almhol-resistant concentmte W C ) at sia-percent concentration. There are, however? ARC foam concentrates designd to be used at three-percent concentration on polar solvem.

Pmprdon on mmns the percentage of ham that is proporrloned into the water. For example, a three-percent fmmpmprtioningmeansthatthreeperaeotofthe~foad water solution is foam concentmte and the remaining 97 percent is water. The foam solution appbtim & L a function dtfiellquid~cearea.ks~therimdfues,don~ attempt to the fire until it is am6rmed that bath the water and foam supply rehbility and @ty can k supplied for the time needed to ex&hguish the frre. The formula to determine the required foam solution Is as

follows: [(Q.8) x (Tank diametd)] x (0.26 gpm per square foot) x (60 or 120 minutes) = Total foam solution required in gallons.'

The application rate (0.26 g p per square foot) and time frame (60 or 120 minutes) used above are tht latest figures uxd by the LASTFIRE project arrd British Petroleum (BPI. When using pmtable/mobile foam monitors, BP recommends planning for a foarn rate production of 0.26 gpm per square fmt, which is an inease by 160 percent of minimum NFPA rates.* This allows for the loss of foam that. Eails to reach the tank interior or breaks down bemuse of heat and thermaI currents. Rerent major fires and the resulting oonsemus of lea* industry experts have confirmed that higher applimtion rates are required. It b g a d y accepted that appliation rates will vary depending on the tank diameter (surface area). For --tank diameters, a higher application rate is required. Industry experts have previously recommended the following rates:

Tank Diameter (feet) Application Rate (gpmlsq-ft.) Up to 150 0.16 150 to 200 0.18 201 to 250 0.20 251 to 300 O R 2 More than 300 0.24 or higher

74 November 2008 FIRE €NC)WEERINQ

In addition to the recommmdatlons of the December 2005 WXHRE Updaw (9, it. is an accepted practice chat the foam supplies on hand to maintain continued suppression equal at 1- the amount used for initial exthgubhrnent. My personal viewpint is to calculate high so that adequate supplies and resources are available. You can a h q s return unused supplies to the warehouse, but if the supplies are not M b l e , then the fm may not be extinguished. Although these application rates and timeframa appear

daunting, fire departments must understand that although large quantities of foarn supplies are required for large tanks, hdhidual departments do not always have to stock such large quantities. Innovative so1utions, such as regional foam coop eratives, industry paamemhips, task force concepts, or private contractom, may be the soIution. Some of the calculated flows m y reach in excess of 10,000 to 18,000 gpm and require large &livery devices such as trailer-mounted monitors and large

p o d l e Pumps. D u r i n g t a n k f m , p l a n t ~ e I ~ ~ d p u m p

ing product out of the involved tank. Note that wand- ~ c t o u t o f ~ t a l l k ~ l y n d g h t n o t b e t h e b e s t a p tim. T d g pduct from tfxe burning (or exposure tank1 in- the amount oftank steel expo& to the fire. With the product inside the tank, the liquid 5 acdng &e a hat sink and i S p ~ t h e t a n k ~ U w a n E n r m b e i n g ~ ~ t 0 the he. Depending on the situation, you might not want to d- low tfie plant to pump product out, or you may decide to allow product to be pumped in. Consult with plant operatiom personnel a d include them in your on-scene planning process.

8 L Q C O V ~ FROnrOVEr2. AND BOtlOvlR CetZain phenomena need to be defined: sIopwer,

hthcwer, and boilover. A slopwer results when a water stream Is applied to the hot surface of burning oil, causing the burning oil to slop over the tank sides. A frothover is the overtlowing of a container not on j5re when water hils under the surface of viscous hot od. An example is hot asphalt loaded into a tank contairiing some water. The water may become heated and start to Ml, causing the asphalt ta overflow the tank.

Compare these events with the defmition of a boilover: a sudden and violent ejection of crude oil (or other liquids) from the tank resulting from a reaction of the hot layer and the accumulation of water at the bottom of the tank. A boilover occurs when the residues (heavier particles remaining after combustion3 from the burning surface become more dense than the surroun.&g, less dense oil, and the residues sink down below the &ace level toward the bottom of the rank. As the hot layer d mwe dense, burned oil mwes down- ward, and this uheat-wve" will eventually reach the water that normally acmmulates at the bottom of a tank. When the two meet, the water is superheated and subsequently boils and expands explosidy, causing a violent eJectian of the tank contents. Although the normal wa~r--steam apansion ratio is 1,700:1, this is at 212OF. At higher temperatures, the water- * s ~ a p a m h n ratio can k as much as 2,300:l at 500°F.

If a boilover occurs, a ruled-thumb says that the expelled

or the

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STORAGE TANK FIRES crude oil may travel up to 10 times the tank diameter arnund the tank perimeter. As an example, in a crude oil tank

that is 250 feet in diameter, expect crude oil to cr)ver an arca of 2.500 feel from ihe tank. lhesc figures have never been tested for very large atnlospheric storage

tanks of 300 feet or greater, so in tanks of this size, the distance of 10 times the tank diameter may have to he incrcased. Therefore, carefully consider the location

of the incident command post, staging, cquiprnerlt placemmt, medical triage,

and a safe zone Identify and use additional fircfigl~t-

ing resources. Local plnnt fire brigade

members can prclvidc the much-needed supporl and technical advice. Many of ihe hardwarc resources may be avaifahlc. at the facility or through industrial and municipal mutual-aid agreements. Solnc facilities havc contracts with private third-party companies that specialize in extinguishing large hydrocarbon fires.

FIREFIGHTING STRATE61ES Firefighting strategies and tactics are

also important. Evaluate the objecti~es or goals vs. the risk. Strategies include the following:

Nonintervention. This is essentiafly

a nonaction mode whcn the risks associatetl with intervening are

unacceptable. All personnel are withdrawn tcl a safc area. Defenhive. In this tactic, certain areas may be conceded to the incident, and actions are limited tn protecting exposures and limiting

thc sprcad of the incident. Offensive. Aggressive and direct tactics used to control an incident.

A s with most fires, the benefits must

outweigh the risk. If a small-diametcr

tank is burning w i ~ h no threat to exposures, should you extinguish the fire? If the tank haa already lost its contents, is

exposure protection more appropriate? These considerations are identifietl and developed as part of the preincident re-

sponse planning, dwcloprnent of emergency action plans, and the identification of the credihlt. incident scenarios.

Environnwntal conditions such as

wind and rain could create prt3hlcms

with distance/range of the water/ Foam solution streams. Changes in

wind direction might causc corrections to incident action plans with respect to changes in staging locations. An incrcase in temperature or humidity could force a quicker rotation of fire-

fighters to prevent heat stresses.

ADDITIONAL C O U S I ~ R A ~ W Consider the following additional re-

sponse and r)perational conditions when

preparing preincidcnt resporlse plans and incident aaion l~latls:

Inrcroperability. Identify these issues during prcincident response planning. Ensure inferoperability of the plant facility's fire water and extinguishing systems, the mutual- or automatic-aid del~artments, and the third-party cmcrgency response contractors that may be on retainer tr) re-

spond to a plant facility to assist with storagc tank fires or emergencies.

Foam supplies. Consider regional foam cooperatives to establish suficienr

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foam mncentmte shpplb h~ 1- storage tank h s or emergencies. R e m w , &kknt foam concamate supplies are not enou&;tWam+m be latge-volume monitm md large-volume h e w supply t h e . w a ~ - d foam sbIuti~~s r e q u k d t a ~ t h e ~ r g e a q . -

ask farces. Consider preestab- lishing iaduswial emergency task forces to respond to such incidents. They wwld he predetermined and activated to suppiy stafling, equipment, foam concentclh~ and appara- .tus to miiigate emergency sceoslrias at stgtage tank h a - tmns. IGs a n then call -it task force or multiple task forces, knowing that the personnel, equipment, and apparams r e q u i d will respond. These task forces would be identified in the p h i d e n t response plans.

' f 2 x i r d - g ~ c r ~ ~ ~ ~ i n ~ ~ t y p e s ~ f iplddenb should be Werrrified and ammunimted with; you n e e d t P l e m t o ~ ~ ~ e 8 e ~ b ~ c ; l n ~ f a ; r m supplies, subject mattef m m X % and equipment IW ~~ a ~ b k o n a d a p ~ ~ ~ i s i n a c i t y o r ~ .

Gpedalhd ind- fire tddng. Fire departments &odd consider sending personnel to specializd Indus- M a 1 fire training programs su they can learn more about stofage ti^& fiMghtiig and emergency incidents. National Pro-Board certikation in storage tank emagencies is mw avaiIab1e at some training centers. If yw have storage tanks In your area, %exril persome1 to spwdid training, Of bring in subjm matter exptfts to delhrer tbhing in-house.

Ahugh your training focuses on the bread-butter o p m t i ~ l l ~ in your &stria you must also train an h- f t e - qpencyhigkid scenarios. M coutmnm- AS part of the equipment newwry

- w delivex foam dudon% to the point of oper&msJ seriously cmde$ jet rado mtrollers. Normally, foam foamconcentrate must k p W withia a specified, &tame from the mde, usually 1 5 0 k ~ U ~ g a ~ f 8 C i o ~ n w ~ ~ a r n a ~ ~ ~ , t h t 3 e a f f o m m n n m b e p h o e d ; 3 8 f a r a ~ ~ 2,500 feet fmm t b ~ nozzle. Jet ratio cmtmUler$ are mturi- qpe devices that move *t conmawate b r n a mate storage- 1-n ta the matched foam d e .

FQam qWntid43. Large qummes of ham combate will be m. For large incidents, using 55-gaUm drums is not recommndedj 275-n tcrtes. and f;uge bm& are the @emel ham coxlcentrate ddivery methods, During prehcidmt response plambg as well as during rhe incident, eduate the logistics of moving the fogm concentrate ta the

point of foam injection. If h e a w ~ s routes are Hocked with vehids and hose, how crmn you get the conwntrate to where it needs to be? AdWody, how dl the foam be tmans- f emd~romtheco~eratothewaters tre&This~k the makest link in & chain. Although you have the kpt containers with the best foam oil-e am2 la poaithq If you are missing the $4 wrench Ch;tt opens the containers, you just bmverylarge matracks, beawert3atisallyouc;lnusethe m~ftahersfor.Wh&isyow~stlhk?~emer&er,,theIIttle

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"reasing" the fire. &fore attacking a tank fire fully, practice 'teasingn the fire. When first applying water to a storage tank fire, the cold water strik- ing the burning fuel surface will react, increasing the intensity of the fire. To prevent a more violent reaction, pass the extinguishing smams over the top of the tank until the fire settles back

all personnel of them during safety briefings. Two esolpe routes must be identified and lead to safety zones where accountability can be vwicied.

Establish safety zones upwind and uphill of the Incident. Vwify personnel accountability at these locations. In addition, designate a clear evacuation route from this safe area so that personnel mn be further evacuated from the safety zone if conalitions deteriorate to a level

... Fires involving large aboveground

storage tanks can be extremely costly in terms of property damage, environmental concerns, and public impact. Additionally, the control and extinguishment of full-surface tank fires require a large amount of cornmitrnent in humar~ logistics and equipment resources. Tank fires are complex events. Fighting them rmuires irn~lementation nf nlans. nwna-

I I - . - - -. =-- - . -.-= --"-. -- r----, r- -r-

down. At this point, a full attack should that makes this area unsafe. ration, and proper use of resources w r - begin with a foam solution. The term I - -

"teasing" the fire is generally credited I to Dwight Williams of Williams Fire & Hazard Control, which specializes in 1 fighting storage mnk fires. WiIliams Fire & Hazard Control has extinguished the largest storage tank fire (270 feet in diameter) to date.

Foam appfication. Do not position extinguishing streams around the !

I

tank for multiple points of application. Position foam monitors at one location; the foam streams should enter the tank at the same point and impinge on the surface in the same area. This will help achieve a stable foam bhnkt more quickly. This foam blanket will then

I I

spread out from this c m t d point on I

the surface. Do not be tempted to move the streams to other positions. If no a p preciable lessening of the fire intensity

I occurs within the first 20 to 30 minutes, instead of moving the stream position, review the rate of applimtion.

I I I 1 LCES. When developing an inci-

dent action plan, consider the acronym LCES Qookouts, communications, escape routes, and safety zones).

lookouts must be experienmcl and be able to see the fie and firefightem, and they must be able to recognize risks to fwdighters. They must be the IC's additional eyes and a. Post them in strategic areas so they mn notify the IC of any relevant information or change in conditions.

Maintain communications with all personnel operating on the scene, plant operations personnel, and subject mat- tex expert$. You must keep pmonnel operating in remote Iomtions informed of any change to operational tactics. Lookouts must maintain communications with operating persamel also.

Establish escape routes and infornD

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difiared by an fictive emergency mawgem- Instmion of Chernial En ' n m IlChernq. 8P Races Safety Sen'= Fire safety h&et liquid &mhon Tank /?re: P m t i m and Rev-.

Only with and ddls dl YQW -ent kcOme Rugby, Kingdom: )ChemE 2005,

proficient in the mtegies and needed to succesm~ I n a o n af Charnk[ Engineea [IaemEj, Foam Ap ,;cat;on for fight a storage tank fire. FullSvrface Tack F i e - king Mobile Equipnenr RQ$ United Kingdwn:

IChemE, no date.

M F I R E Pro'ea. LASFIRE Update: Risk Redudon Options U n d ENDNOTES a n d m : L4m IRE row, m. 7 . A g d a i c h m e is a m ~ d e d s i rm~re made of short, straight, triangu- CH, AR Markley, ,ma, lirefiwng for wFIidpa, Fjm lar sectiws that fom p o b n s . These l i g M ht domes can span l a y *noes and are used on stwage tanks to A c e vapdr missbra and to Wm Tuhl OK: fire Enginewingo 2007. ,

p tec t from weather. They p r e a snow acrurnulati& on floating roofs and re&& rainwater ammulation as well. I 2. M R R E is a conschum of international ail corn nies reviewin the r i i a a a i a t e d with fires in storage tanks and deve$ing h e best?ndustly practices to mitigate the risk I 3 Hitdebraid, M.S. and G.G. Noll, %rage Tank Emergedes. hmpolis, Mi3 k i Hat, 1997. I 4. The LASTFlRE Update (December MD5) states h t i d standards [NFPAI require at 1-65 rninukr ofwerating time. KEfire has beeo burning fw some time, this shauld be increasedm at le&l2(1 minutes," 15. I 5. Bri&h P&leum (BP) offers a ba rn ap lidor estimator, a quick calcula- tor fa defermining the foam a&tion at w a g e tank firer I BlBtlW3RAPHY American Petroleum Institute (#I). API 2021 a: Intdrim Study P m t i o n

offires in la Abowgmund A h m p M c Storage ~ , " 2 . ~ m , oC: MI , 1%.

Hildebrand, MS and GG Ndl, Shrage Tank Gnergem'e~ Guidelines and P d r e s . Annapdis, MD: R d Hat, 1%'.

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Storage Tank Fires